A look at the contents of the /25 is puzzling, because I can see almost 1500 sites [csv] on a number of active IPs [txt], almost none of which have any kind of discernible web presence or reputation.

Drilling down into the domains and registrants [csv] shows a list of either Chinese or US registrants, but in the vast majority of cases they look to be fake. The key indicator is that the email addresses listed are all of a similar format and bear no relationship whatsoever to the name of the registrant.

The random structure of most of the domains is an indicator of possible maliciousness. The few domains that don't meet these pattern seem to be .fr domains which look like they have been hijacked or re-registered.. and oddly they are all registered to different (often obviously fake) people at the same address in France:

My personal opinion is that there is enough evidence to treat 104.152.215.0/25 as a suspect network. It does not appear to have any legitimate sites, the sites that do exist are of an unknown purpose and often have apparently fake WHOIS details for the domains.

Blocking or monitoring for traffic to and from that /25 is the easiest way of doing it, alternatively these are the domains being used in this network block: